Dempsey Steven J, Gese Eric M, Kluever Bryan M, Lonsinger Robert C, Waits Lisette P
Department of Wildland Resources, Utah State University, Logan, Utah, United States of America.
United States Department of Agriculture, Wildlife Services, National Wildlife Research Center, Department of Wildland Resources, Utah State University, Logan, Utah, United States of America.
PLoS One. 2015 Oct 14;10(10):e0138995. doi: 10.1371/journal.pone.0138995. eCollection 2015.
Development and evaluation of noninvasive methods for monitoring species distribution and abundance is a growing area of ecological research. While noninvasive methods have the advantage of reduced risk of negative factors associated with capture, comparisons to methods using more traditional invasive sampling is lacking. Historically kit foxes (Vulpes macrotis) occupied the desert and semi-arid regions of southwestern North America. Once the most abundant carnivore in the Great Basin Desert of Utah, the species is now considered rare. In recent decades, attempts have been made to model the environmental variables influencing kit fox distribution. Using noninvasive scat deposition surveys for determination of kit fox presence, we modeled resource selection functions to predict kit fox distribution using three popular techniques (Maxent, fixed-effects, and mixed-effects generalized linear models) and compared these with similar models developed from invasive sampling (telemetry locations from radio-collared foxes). Resource selection functions were developed using a combination of landscape variables including elevation, slope, aspect, vegetation height, and soil type. All models were tested against subsequent scat collections as a method of model validation. We demonstrate the importance of comparing multiple model types for development of resource selection functions used to predict a species distribution, and evaluating the importance of environmental variables on species distribution. All models we examined showed a large effect of elevation on kit fox presence, followed by slope and vegetation height. However, the invasive sampling method (i.e., radio-telemetry) appeared to be better at determining resource selection, and therefore may be more robust in predicting kit fox distribution. In contrast, the distribution maps created from the noninvasive sampling (i.e., scat transects) were significantly different than the invasive method, thus scat transects may be appropriate when used in an occupancy framework to predict species distribution. We concluded that while scat deposition transects may be useful for monitoring kit fox abundance and possibly occupancy, they do not appear to be appropriate for determining resource selection. On our study area, scat transects were biased to roadways, while data collected using radio-telemetry was dictated by movements of the kit foxes themselves. We recommend that future studies applying noninvasive scat sampling should consider a more robust random sampling design across the landscape (e.g., random transects or more complete road coverage) that would then provide a more accurate and unbiased depiction of resource selection useful to predict kit fox distribution.
用于监测物种分布和丰度的非侵入性方法的开发与评估是生态研究中一个不断发展的领域。虽然非侵入性方法具有减少与捕获相关的负面因素风险的优势，但与使用更传统侵入性采样的方法的比较却很缺乏。历史上，敏狐（Vulpes macrotis）栖息于北美洲西南部的沙漠和半干旱地区。该物种曾是犹他州大盆地沙漠中数量最多的食肉动物，如今却被视为稀有物种。近几十年来，人们一直试图对影响敏狐分布的环境变量进行建模。我们利用非侵入性粪便沉积调查来确定敏狐的存在，使用三种常用技术（最大熵模型、固定效应和混合效应广义线性模型）对资源选择函数进行建模，以预测敏狐的分布，并将这些模型与通过侵入性采样（来自无线电项圈狐狸的遥测位置）开发的类似模型进行比较。资源选择函数是利用包括海拔、坡度、坡向、植被高度和土壤类型在内的多种景观变量组合开发的。所有模型都以随后的粪便收集作为模型验证方法进行了测试。我们证明了比较多种模型类型对于开发用于预测物种分布的资源选择函数以及评估环境变量对物种分布的重要性的重要性。我们研究的所有模型都显示海拔对敏狐的存在有很大影响，其次是坡度和植被高度。然而，侵入性采样方法（即无线电遥测）在确定资源选择方面似乎更好，因此在预测敏狐分布方面可能更可靠。相比之下，由非侵入性采样（即粪便样带）创建的分布图与侵入性方法有显著差异，因此粪便样带在用于占用框架以预测物种分布时可能是合适的。我们得出结论，虽然粪便沉积样带可能有助于监测敏狐的丰度以及可能的占用情况，但它们似乎不适用于确定资源选择。在我们的研究区域，粪便样带偏向于道路，而使用无线电遥测收集的数据则由敏狐自身的活动决定。我们建议未来应用非侵入性粪便采样的研究应考虑在整个景观中采用更稳健的随机采样设计（例如，随机样带或更完整的道路覆盖），这样将能提供更准确且无偏差的资源选择描述，有助于预测敏狐的分布。
